code: def test_default_ioctx(self):
      # Test DatasetReader without passing in IOContext
      input_config = {"format": "json", "paths": self.dset_path}
      config = AlgorithmConfig().offline_data(
          input_="dataset", input_config=input_config
      )
      dataset, _ = get_dataset_and_shards(config)
      reader = DatasetReader(dataset)
      # Reads in one line of Pendulum dataset with 600 timesteps
      assert len(reader.next()) == 600
  
imports: import tempfile
  import os
  from pathlib import Path
  import unittest
  import pytest
  import ray
  from ray.rllib.algorithms.algorithm_config import AlgorithmConfig
  from ray.rllib.offline import IOContext
  from ray.rllib.offline.dataset_reader import DatasetReader, get_dataset_and_shards, _unzip_if_needed
label_desc: Use image node_id 10 for calling the TestDatasetReader obj's underlying member method code with example usage: obj.test_default_ioctx() without return types